Tubing



R. M. FRINK Sept. 24, 1963 TUBING Filed 001;. 5, 1959 FIG.2.

u? a O lu F KI m N N I mm m m m u/ s w United States Patent 3,104,464 TUBING Russell M. Frinlr, Bloomfield Hills, Mich, assignor to Calumet & Hecla, Inc., Allen Park, Mictn, a corporation of Michigan Filed Oct. 5, 1959, Ser- No. 844,330 8 Claims. ((31. 29566) The present invention relates to the manufacture of tubing and more particularly, to an operation in which relatively heavy walled tubular stock is first flattened and thereafter rolled in such a way as to increase its length and decrease its thickness without substantially increasing its width. This flattened and rolled stock is thereafter expanded or re-forrned into tubular shape.

The present invention is concerned with apparatus and a method for expanding or reshaping the flattened rolled stock into a tubular condition.

It is an object of the present invention to provide a mandrel adapted to be torced through the flattened tubing to open up the tubing into tubular form.

More specifically, it is an object of the present invention to provide a floating mandrel adapted to open up and expand flattened tubing into generally tubular form, in combination with a die having an opening somewhat smaller than the outside diameter of the tubing as expanded by the mandrel to prevent passage of the mandrel through the die.

It is a further object of the present invention to provide a mandrel having a flattened chisel point at its leading end to enter into flattened tubing, said mandrel having a cylindrical trailing portion and an intermediate portion merging from the chisel point leading edge to the cylindrical portion in such a way as to provide a controlled expansion or opening up of the tubular stock.

It is a further object of the present invention to provide a mandrel as described in the preceding paragraph having gradually converging edge portions of arcuate cross-section formed to a radius substantially equal to the final internal radius of the fully opened up or expanded tube.

wide chisel portion to the circular trailing portion operates to prevent movement of the mandrel through a die having an opening equal to the diameter of the circular trailing portion of the mandrel plus twice the thickness of the tubular stock.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating preferred embodiments of the invention, wherein: 7

FIGURE 1 is a fragmentary perspective view of tubular stock from which the tubing is produced.

FIGURE 2 is an end view of the stock shown in FIG- URE 1 after it has been flattened.

FIGURE 3 is a view of the stock shown in FIGURE 2 after it has been rolled to reduce its thickness and to elongate it without substantially changing the width of the flattened stock.

FIGURE 4 is a fragmentary side elevation with parts in section showing a floating mandrel, a die, and rollers for drawing the stock through the die.

'as indicated at 30, is cylindrical.

, 3,104,464 Patented Sept. 24, 1963 FIGURE 5 is an enlarged section on the line 55, FIGURE fl.

d FIGURE 6 is a plan view of a modified form of man- FIGURE 7 is a. side elevation of the mandrel shown in FIGURE 6.

FIGURE 8 is a diagrammatic view showing a plurality of superimposed sectional shapes of the mandrel of FIG- URES 6 and 7, taken substantially on the lines aa, bb, and 0-0.

FIGURE 9 is an axial section through a die in which tubular stock is opened up by means of the mandrel shown in FIGURES 6 and 7.

Referring first to FIGURES 1-3, a section of tubular stock 10 is shown in FIGURE 1 having a relatively thick Wall section. In carrying out the present invention this tubular stock is flattened as indicated in FIGURE 2 to form the flattened stock 12 in which the opening 14 through the tube now appears as a closed slit 16. The relatively thick stock 12 of FIGURE 2 is now rolled longitudinally to produce the relatively thin flattened and rolled stock 18. This reduces the thickness of the stock and accordingly reduces the wall thickness of the tubing as shown. This rolling is carried out insuoh a Way as to maintain substantially constant width in the rolled stock and accordingly, the reduction in thickness results in a corresponding elongation of the stock.

This stock may be shipped in flattened condition either rolled or straight, and before use it is opened up or expanded to again assume a substantially tubular condition.

The present invention relates to the method and apparatus of opening up or expanding the tubular stock. As illustrated in FIGURES 4 and 5, this is accomplished by means of an expander 20 and a floating pin 22 which parts as shown in FIGURE 4, are separate but which may if desired be combined into an integral unit. The pin 22 is of circular cross-section throughout and hence it will be observed that the right hand portion of the pin 20, as seen in FIGURE 4, is in effect of conical shape. The expander 20 has a cylindrical trailing portion 24. The leading end of the pin 22 has :a cylindrical portion 26 of the same diameter as the cylindrical portion 24 of the expander 20, and a tapered following portion 28 of conical shape. Preferably, the trailing end of the pin 22, Associated with the mandrel assembly made up of the expander 20 and pin 22 is a die 32 having an opening 34 of a size small enough to prevent movement of the pin 22 therethrough.

In operation the mandrel assembly is forced into one end of the flattened stock 18 far enough to permit the end of the opened up tubing to be gripped between a pair of rolls 35 provided with concave peripheral grooves 36. The rolls are then driven in the direction indicated by the arrows, drawing the tubular stock through the die. Inas- :much as the enlarged intermediate portion of the mandrel assembly made up by the cylindrical portions 22 and 24 of the pin and expander respectively, cannot pass through the die opening 34, the mandrel assembly floats in the relationship shown.

From an inspection of FIGURE 4 it will be seen that the tubular stock is not only fully opened up, but it is expanded to a somewhat greater diameter than its ultimate shape. Thereafter, the expanded tubular stock is reduced to pass through the die and its internal diameter and external diameter are determined by the corresponding diameter of the trailing end 30 of the pin 22 and the diameter of the die opening 34.

Manufacture of tubing in accordance with the foregoing produces a finished tube having a pair of radially outwardly projecting axially extending tins as is well understood, and a portion of one of these fins is indicated at 48 in FIGURES 4 and 5.

Details of a preferred form of floating mandrel are illustrated in FIGURES 6-8. In these figures the floating mandrel is illustrated at 59 has a cylindrical trailing or finishing portion 52 and a leading or entering portion 54 which as best seen by a comparison of FIGURES 6, 7 and 8 comprises a knife edge 56 of a width dimensioned to extend substantially the full length of the closed slit 16, the corners being rounded off as. indicated at to facilitate entry of the mandrel into the flattened and rolled tubing.

From the entering knife edge to the trailing cylindrical portion 52, the portion 54 of the mandrel has a shape which increases progressively in thickness and decreases progressively in width as shown by the successive sections a, b, and c of FIGURE 8, taken on the section lines a-a, 12-5, and c-c of FlGURE 7. It will be observed in FIGURE 8 that at the progressively thicker and narrower portions of the mandrel, the edge surfaces designated 60, 62 and 64- are all of a transverse curvature having a radius equal to the ultimate radius of curvature of the cylindrical inner surface of the finished tube.

The advantage of this construction is that as the closed slit is initially opened, its extreme ends are initially shaped to the final cylindrical curvature at a time when forces are most readily available to move the wall poo tions apart through an angle of approximately 180 degrees to change from the closed slit end to the cylindrical surface desired in the finished tube. The width and thickness of the portion 54- of the mandrel are designed so that the straight portions of the tube interconnecting the curved end portions during expansion of the tube from the closed position of FIGURE 3 to the fully expanded position illustrated in FIGURE 5, are maintained under tension.

With this arrangement movement of the mandrel through the die 66 is of course prevented due to the fact that the tapered portion 54 has one dimension greater than the final diameter of the internal surface of the finished tubing. This avoids the expansion of the tubing beyond its ultimate desired diameter, followed by a re duction in diameter in the die.

The drawing and the foregoing specification constitute a description of the improved tubing in such full, clear, concise and exact terms :as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. The method of opening up flattened tubular stock which comprises initially shaping the flattened edge portions of the tubing to the desired radius of curvature, and progressively shaping circumferentially adjacent portions thereof into the desired radius of curvature until the entire tubing is of circular cross-section.

2. Floating mandrel means for use in conjunction with a die having a circular opening to open up flattened tu bing, said mandrel means having a leading knife edge portion of a width substantially equal to the width of the opening in the flattened tubing, a trailing portion of circular cross-section dimensioned to be retained within the circular die opening and to cooperate therewith to produce the required diameter and wall thickness of the tin ished tubing, the intermediate portion of said mandrel means being of progressively increasing thickness and progressively decreasing width, the width of the intermediate portion of said mandrel means being greater than the diameter of the said trailing portion thereof.

3. Floating mandrel means for use in conjunction with a die having a circular opening to open up flattened tubing, said mandrel means having a leading knife edge portion of a width substantially equal to the width of the opening in the flattened tubing, a trailing portion of circular cross-section dimensioned to be retained within the circular die opening and to cooperate therewith to pro duce the required diameter and wall thickness of the finished tubing, the intermediate portion of said mandrel means being of progressively increasing thickness and progressively decreasing width, the width of the intermediate portion of said mandrel means being greater than the diameter of the said trailing portion thereof, the edges of the intermediate portion of said mandrel means being of a transverse curvature throughout approximately circular die opening and to cooperate therewith to pro duce the required diameter and wall thickness of the finished tubing, the intermediate portion of said mandrel means being of progressively increasing thickness and progressively decreasing Width, the width of the inter mediate portion of said mandrel means being greater than the diameter of the said trailing portion thereof, the

edges of the intermediate portion ofsaid mandrel means being of a transverse curvature throughout approximately f equal to the ultimate internal radius of curvature of the finished tubing, the intermediate portion of said mandrel means having a peripheral dimension in any plane perpendicular to its axis substantially equal to the internal circumference of the finished tubing.

5. The method of opening up tubing flattened to have creased edge portions connected by flat side portions which comprises initially shaping the opposite creased edge portions to the final desired radius of curvature while separating the side portions connecting said edge portions in substantially parallel relation to each other, and progressively extending the curved edge portions to include more and more of the opposite flat side portions until the tube has reached substantially complete continuous curved cross-sectional shape.

6. The method of opening up tubing flattened to have creased edge portions connected by flat side portions which comprises drawing the flattened tube over a mandrel having a knife-edged leading edge of a width substantially equal to the internal width of said tubing in flattened condition, and having a gradually increasing thickness up to approximately the internal diameter of tlhe tubing when fully opened up to generally cylindrical s ape.

7. The method of opening up tubing flattened to have creased edge portions connected by flat side portions which comprises drawing the flattened tube over a mandrel having a knife-edged leading edge of a width substantially equal to the internal width of said tubing in flattened condition, and having a gradually increasing thickness up to approximately the internal diameter. of

the tubing when fully opened up to generally cylindrical i if I shape, the opposite edge portions of the mandrel from its knife edge to a portion thereof of circular crosssection being of arcuate cross-section having a radius of;

drel having a knife-edged leading edge of a width sub-; stantially equal to the internal width of said tubing in flattened condition, and having a gradually increasing thickness up to approximately the internal diameter of the tubing when fully opened up to generally cylindrical shape, the opposite edge portions of the mandrel from its knife edge to a portion thereof of circular cross section being of arcuate cross-section having a radius of curvature approximately equal to the internal radius of the fully expanded tubing, the inner cross-sectional perimeter of the mandrel in all planes between its entering knife edge and its circular cross-sectional portion being at least equal to the internal circumference of the openedup tubing whereby the material of the tubing is maintained in continuous circumferential tension.

References Cited in the file of this patent UNITED STATES PATENTS Sharp Nov. 11, Westin J an. 20, Staples et al. June 9, Wadell Oct. 3, Kerr May 12,

FOREIGN PATENTS Great Britain Mar. 6, Great Britain Nov. 2-0, 

2. FLOATING MANDREL MEANS FOR USE IN CONJUNCTION WITH A DIE HAVING A CIRCULAR OPENING TO OPEN UP FLATTENED TUBING, SAID MANDREL MEANS HAVING A LEADING KNIFE EDGE PORTION OF A WIDTH SUBSTANTIALLY EQUAL TO THE WIDTH OF THE OPENING IN THE FLATTENED TUBING, A TRAILING PORTION OF CIRCULAR CROSS-SECTION DIMENSIONED TO BE RETAINED WITHIN THE CIRCULAR DIE OPENING AND TO COOPERATE THEREWITH TO PRODUCE THE REQUIRED DIAMETER AND WALL THICKNESS OF THE FINISHED TUBING, THE INTERMEDIATE PORTION OF SAID MANDREL MEANS BEING OF PROGRESSIVELY INCREASING THICKNESS AND PROGRESSIVELY DECREASING WIDTH, THE WIDTH OF THE INTERMEDIATE PORTION OF SAID MANDREL MEANS BEING GREATER THAN THE DIAMETER OF THE SAID TRAILING PORTION THEREOF.
 5. THE METHOD OF OPENING UP TUBING FLATTENED TO HAVE CREASED EDGE PORTIONS CONNECTED BY FLAT SIDE PORTIONS WHICH COMPRISES INITIALLY SHAPING THE OPPOSITE CREASED EDGE PORTIONS TO THE FINAL DESIRED RADIUS OF CURVATURE WHILE SEPARATING THE SIDE PORTIONS CONNECTING SAID EDGE PORTIONS IN SUBSTANTIALLY PARALLEL RELATION TO EACH OTHER, AND PROGRESSIVELY EXTENDING THE CURVED EDGE PORTIONS TO INCLUDE MORE AND MORE OF THE OPPOSITE FLAT SIDE PORTIONS UNTIL THE TUBE HAS REACHED SUBSTANTIALLY COMPLETE CONTINUOUS CURVED CROSS-SECTIONAL SHAPE. 